Americans Exposed to Atomic Bomb Levels of Radiation through Medical Imaging, CT Scans, Mammograms

Part 2 A Reader wrote me following my first post on the subject :

” I am not defending CT scans, but you cannot compare radiation exposure from a nuclear weapon to that received from a CT scan. Why? Because the Hiroshima / Nagasaki victims, along with their initial blast exposure, ingested radioactive stuff that lodged in their tissues (lungs, thyroid, etc) and sat there for years.

Each particle may have had, in itself, relatively low radiation output, but it sat there for years next to healthy tissue. CT scans give you one blast (or a several minute blast) and are then gone.

Actually I do and I compare as the authors of the research.

For example, a scan of the head delivers 100 times more radiation than a chest X-ray, and an abdominal scan is equivalent to about 500 chest X-rays!

And a barium swallow — a procedure used to screen the upper gastrointestinal tract — delivers the radiation equivalent of 150 chest X-rays, which is only a fraction of the amount of radiation delivered during a typical abdominal CT scan.

A typical chest CT means around a 175-times-greater dose of radiation than a similar chest X-ray—that’s like 20 sets of mammograms.

X-rays can also ionize DNA directly. Most radiation-induced damage is rapidly repaired by various systems within the cell, but DNA double-strand breaks are less easily repaired, and occasional misrepair can lead to induction of point mutations, chromosomal translocations, and gene fusions, all of which are linked to the induction of cancer.

I cite :

“Most of the quantitative information that we have regarding the risks of radiation-induced cancer comes from studies of survivors of the atomic bombs dropped on Japan in 1945.25 Data from cohorts of these survivors are generally used as the basis for predicting radiation-related risks in a population because the cohorts are large and have been intensively studied over a period of many decades, they were not selected for disease, all age groups are covered, and a substantial subcohort of about 25,000 survivors26 received radiation doses similar to those of concern here — that is, less than 50 mSv.”

There was a significant increase in the overall risk of cancer in the subgroup of atomic-bomb survivors who received low doses of radiation, ranging from 5 to 150 mSv (1) (2) (3) (4) the mean dose in this subgroup was about 40 mSv, which approximates the relevant organ dose from a typical CT study involving two or three scans in an adult.”

Although most of the quantitative estimates of the radiation-induced cancer risk are derived from analyses of atomic-bomb survivors, there are other supporting studies, including a recent large-scale study of 400,000 radiation workers in the nuclear industry (5) who were exposed to an average dose of approximately 20 mSv (a typical organ dose from a single CT scan for an adult). A significant association was reported between the radiation dose and mortality from cancer in this cohort (with a significant increase in the risk of cancer among workers who received doses between 5 and 150 mSv); the risks were quantitatively consistent with those reported for atomic-bomb survivors.

Source : http://content.nejm.org/cgi/content/full/357/22/2277

(1) Preston DL, Pierce DA, Shimizu Y, et al. Effect of recent changes in atomic bomb survivor dosimetry on cancer mortality risk estimates. Radiat Res 2004;162:377-389
(2) Preston DL, Shimizu Y, Pierce DA, Suyama A, Mabuchi K. Studies of mortality of atomic bomb survivors. Report 13: Solid cancer and noncancer disease mortality: 1950-1997. Radiat Res 2003;160:381-407.
(3) Pierce DA, Preston DL. Radiation-related cancer risks at low doses among atomic bomb survivors. Radiat Res 2000;154:178-186
(4) Preston DL, Ron E, Tokuoka S, et al. Solid cancer incidence in atomic bomb survivors: 1958-1998. Radiat Res 2007;168:1-64.
(5) Cardis E, Vrijheid M, Blettner M, et al. The 15-country collaborative study of cancer risk among radiation workers in the nuclear industry: estimates of radiation-related cancer risks. Radiat Res 2007;167:396-416.

What are some alternatives to CT scanning that patients should know about or ask their doctors?

I would ask if there are ways we can find out the answer without using radiation. Using ultrasound, for example, or doing an MRI scan. Those don’t use ionizing radiation, so there is virtually no risk. And if the scan is definitely going to be done, ask about the dose you will be getting. If a child is getting a scan, a concerned parent should make sure the radiology technician is using the correct pediatric doses.

From Death by Medicine

By Gary Null, Ph.D., PhD; Carolyn Dean MD, ND; Martin Feldman, MD; Debora Rasio, MD; and Dorothy Smith, PhD

Computed Tomography (CT)

The first CT scanner in the US was installed at the Mayo Clinic in 1973. By 1992, the number of operational CT scanners in the US had grown to 6,060. By comparison, in 1993 there were 216 CT units in Canada .
There is little information available on how CT scans improve or affect patient outcomes
In some institutions, up to 90% of scans performed were negative.
Approval by the FDA was not required for CT scanners, nor was any evidence of safety or efficacy.

A recent study by the Massachusetts Medical Society titled, “Investigation of Defensive Medicine in Massachusetts,” concluded that roughly 33 % of the CT scans ordered by obstetrician/gynecologists, emergency physicians, and family practitioners were not motivated by medical need

http://www.ncrponline.org/PDFs/Mass_Med_Soc.pdf

From The US Nuclear Regulatory Commission

The associations between radiation exposure and the development of cancer are mostly based on
populations exposed to relatively high levels of ionizing radiation (e.g., Japanese atomic bomb
survivors, and recipients of selected diagnostic or therapeutic medical procedures). Cancers
associated with high dose exposure (greater than 50,000 mrem) include leukemia, breast, bladder,
colon, liver, lung, esophagus, ovarian, multiple myeloma, and stomach cancers. Department of
Health and Human Services literature also suggests a possible association between ionizing
radiation

http://www.nrc.gov/reading-rm/doc-collections/fact-sheets/bio-effects-radiation.pdf

FDA Public Health Notification: Reducing Radiation Risk from Computed Tomography for Pediatric and Small Adult Patients

http://www.fda.gov/cdrh/safety/110201-ct.html